TK11330BMCL TOKO, TK11330BMCL Datasheet - Page 11

• Manufacturer Part Number: TK11330BMCL
• Description: VOLTAGE REGULATOR WITH ON/OFF SWITCH
• Manufacturer: TOKO

PACKAGE POWER DISSIPATION (P
This is the power dissipation level at which the thermal sensor is activated. The IC contains an internal thermal sensor
which monitors the junction temperature. When the junction temperature exceeds the monitor threshold of 150 C, the
IC is shutdown. The junction temperature rises as the difference between the input power (V
(V
the board material, and the ambient temperature. When the IC mounting has good thermal conductivity, the junction
temperature will be low even if the power dissipation is great. When mounted on the recommended mounting pad, the
power dissipation of the SOT-23L is increased to 600 mW. For operation at ambient temperatures over 25 C, the power
dissipation of the SOT-23L device should be derated at 4.8 mW/ C. The power dissipation of the SOT-89-5 package is
900 mW when mounted as recommended. Derate the power dissipation at 7.2 mW/ C for operation above 25 C. To
determine the power dissipation for shutdown when mounted, attach the device on the actual PCB and deliberately
increase the output current (or raise the input voltage) until the thermal protection circuit is activated. Calculate the power
dissipation of the device by subtracting the output power from the input power. These measurements should allow for the
ambient temperature of the PCB. The value obtained from PD/(150 C - T
pad should provide maximum thermal conductivity in order to maintain low device temperatures. As a general rule, the
lower the temperature, the better the reliability of the device. The Thermal resistance when mounted is expressed as
follows:
For Toko ICs, the internal limit for junction temperature is 150 C. If the ambient temperature, T
P
side is shorted. Input current gradually falls as temperature rises. You should use the value when thermal equilibrium is
reached.
The range of currents usable can also be found from the graph below.
Procedure:
1.) Find P
2.) P
3.) Plot P
4.) Connect P
5.) In design, take a vertical line from the maximum operating temperature (e.g. 75 C) to the derating curve.
6.) Read off the value of P
May, 1997 TOKO, Inc.
D
OUT
is the value when the thermal sensor is activated. A simple way to determine PD is to calculate V
maximum power dissipation, D
D1
X I
T
150 C = 0
0
0
is taken to be P
OUT
JA
JA
J
D1
D
= 0
X P
= 125 C/ P
) increases. The rate of temperature rise is greatly affected by the mounting pad configuration on the PCB,
against 25 C
JA
D1
D
DEFINITION AND EXPLANATION OF TECHNICAL TERMS (CONT.)
X P
= 125 C
to the point corresponding to the 150 C with a straight line.
JA
D
X P
D pd
+ T
P D
D
D
(mW)
D
A
X ( 0.8 ~ 0.9)
D
+ 25 C
against the point at which the vertical line intersects the derating curve. This is taken as the
25
6
3
PD
50
.
D
)
T (°C)
75
5
4
150
A
) is the derating factor. The PCB mounting
IN
X I
IN
A
IN
) and the output power
X I
is 25 C, then:
TK113xxB
IN
when the output
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